This invention relates to the testing of telephone systems in general and more particularly to the testing of conference bridges associated with telephone communication systems.
The present invention is directed to the testing of resistive types of conference bridges which are passive networks of resistors, as distinguished from active conference bridges which include amplifiers and other signal treating devices. The passive type of conference bridge, which is generally well known in the art, is utilized for interconnecting telephone lines or trunks in order to provide telephone conference connections and may or may not be connected to external amplifiers or attenuators. Such resistive bridges are generally arranged to provide equal input and output impedances, generally 600 ohms, and are usually in the form of printed circuit cards inserted into prewired rack assemblies mounted as part of frame mounting terminal blocks in common use in the telephone industry. Such "bridge blocks" are mounted on telephone office frame assemblies and wired into appropriate network trunk lines. In large central offices, several hundreds of such bridge blocks are often mounted in rows on the frames.
The aforementioned conference circuits are utilized extensively for both voice and data applications. Mismatch of impedances, unacceptable levels of cross talk in adjacent lines, significant impairment due to phase delays, line outages, uneven levels of gain or attenuation due to line routing discrepancies, etc., all tend to increase the complexity and cost of providing quality service with reduced downtime. Also, the current growth of conference call connections and interconnection of conference circuits has created operational and service problems that require the use of test equipment for troubleshooting and fault location. The testing procedure is, however, costly and time consuming because of the complexity of conference circuits involved. For example, it is often necessary to locate faults internally within a resistive bridge, such as a burnt out resistor or cold solder joint. More often, however, the fault is external to the bridge on a telephone line connected thereto. In order to check either a conference bridge itself or associated network line, the suspected circuit was heretofore isolated and disconnected from the line. This procedure has involved unsoldering leads from the bridge block in order to tie in or clip on the leads of various test equipment. Because of the close proximity of many connecting points on the terminal block, adjacent circuits are sometime inadvertently shorted out to pose a critical problem in connection with differential data circuits.
It is therefore an important object of the present invention to provide apparatus associated with passive conference bridges through which fault testing may be facilitated and performed without the aforementioned drawbacks.
Another object is to provide a telephone conference bridge circuit that is easy to install and service.